1. Field
The present disclosure relates generally to Integrated Circuits (ICs) in power electronics and, in particular but not exclusively, relates to programming controllers for switch mode power converters.
2. Description of Related Art
Many power electronic IC devices allow selection among two or more functional parameters of the device. Conventional programming methods program these IC devices using resistors or capacitors placed at dedicated terminals of the device. Thus, to program the IC devices, additional terminals may be added to the device for each additional function or programmable parameter, which may translate into increased cost, power consumption, and space required by the device.
One example implementation of an IC having selectable parameters is as a controller for a switch mode power converter. For example, many household and industrial applications require a regulated direct current (dc) power to operate. Since conventional wall outlets generally deliver a high voltage alternating current (ac) power, a power converter, such as a switch mode power converter, is commonly used to transform the ac power into a dc power. These switch mode power converters can be used to convert a low frequency (e.g., 50 Hz or 60 Hz) high voltage ac input voltage to the required level of dc output voltage. Generally, these converters include an IC controller that switches a power switch between an ON state and an OFF state to control the amount of power transmitted to the output of the converter. Various types of switch mode power converters are popular for this use because of their well regulated output, high efficiency, small size, low weight, and their safety and protection features.
Output regulation in a switch mode power converter is usually provided by sensing a feedback signal from the output of the converter and controlling the power converter in a closed loop. The feedback or control signal can be provided by an opto-coupler from a sense circuit coupled to the dc output of the converter or can be extracted indirectly from a third winding magnetically coupled to the secondary winding on the same transformer core. In different control methods, the feedback or control signal may be used to modulate a duty cycle of a switching waveform (referred to as pulse width modulation (PWM)), to change a switching frequency (referred to as pulse frequency modulation (PFM), or to disable some of the cycles of the switching waveform generated by the power converter controller to control the dc output versus load and line variations (referred to as on-off control).